The development of a simple, reliable, inexpensive and environmentally friendly process of silicon etching is of significant practical importance to the semiconductor industry. Various methods of silicon etching were developed in the last three decades
Typically, existing silicon etching methods, involving polishing and texturing, based on PPD is performed in media containing hydrofluoric acid (HF). The etching is combined with the process of photolithography. Such an electrochemical technique involves combining positive (anodic) biasing of the silicon that is exposed to (contacted and wetted by) an aggressive HF etching solution, with possible illumination of the positively biased exposed silicon surface, and is reasonably effective for increasing control and the rate of the silicon etching/texturing process. However, the use of media containing HF is undesirable because it is accompanied by serious environmental issues relating to its handling and disposal.
Slow silicon texturing based on anisotropic etching is usually performed in alkaline solutions that are free from HF, for example, NaOH or KOH solutions, during relatively long term exposure of the silicon surface at open circuit potential (OCP), without electrical biasing. This is because positive (anodic) biasing of silicon in alkaline solutions results in inactivation and/or deactivation of the silicon surface, so that etching, and therefore, texturing or polishing stops. Typical etching rates in KOH at open circuit are below 1 microns/min {e.g., R. A Wind et al., J. Phys. Chem. B, 106, 1557-1569 (2002), I. Zubel and M. Kramkowska, Sensors and Actuators A, Physical, A93(2), 138-147 (2001)}. Attempting to increase the rate of etching and texturing of the silicon by using positive (anodic) biasing of the exposed silicon surface results in working in a region within which the treated material (silicon and/or metal) becomes passive or inactivated, or actively dissolves and becomes deactivated. Thus, except when etching/texturing silicon in HF solutions, positive (anodic) biasing has not been in use.
Thus, it would be highly advantageous to have a method for fast etching (polishing/texturing) a semiconductor material using the technique of positive potential dissolution (PPD), based on applying atypically highly positive (anodic) potentials during conditions of wet etching, and continued etching (polishing/texturing) of a semiconductor material formed therefrom. Such a method is generally commercially applicable to a variety of related fields and sub-fields.